Study puts management of pests to the test

Victoria University of Wellington research into some of New Zealand’s introduced pests has revealed the complexity of managing disease amongst species.

A profile image of Evan Brenton-Rule looking off past the camera, smiling. Behind him are storage boxes and the top of a microscope.

A study by Evan Brenton-Rule, who graduates next week with a PhD in Ecology and Biodiversity, focused on the spread and impact of ants, bees, and wasps.

One of Evan’s main findings showed that the globally widespread invasive Argentine ant may play a role in diseases of honey bees and hive decline. The Argentine ant has been established in New Zealand since 1990.

“Some Argentine ants live together with honeybees in their hives. Hives in the presence of the ants suffered significantly higher mortality rates relative to hives without ants, and always had higher levels of Deformed wing virus,” says Evan.

Deformed wing virus makes the wings of bees shrivel up, and is one of many viruses infecting honeybees around the world.

“It’s possible that the ants are actually carrying the disease of the bees. Another research group at Victoria University of Wellington is now working on confirming this causation, which has potentially big implications,” says Evan.

“There is little in the way of regulations that control the movement of honeybee hives around New Zealand. Different management techniques could be used to help stop the spread of the disease if it is confirmed.”

Evan also studied the spread of German wasps, and used molecular genetic tools to track the likely pathway of populations around the world.

“In some regions there were likely multiple introductions, via various trade pathways,” says Evan. “I also found that four different honeybee viruses were found in German wasp populations worldwide.

“These results highlight how complex managing an invasive species is. The introduction of one exotic species likely brings a range of diseases, which is poorly understood and inconsistently considered in international and regional management plans.”

Evan says legal regulation is often a response once a problem has already arisen.

“At a global level we regulate invasive species relatively well. But as the focus becomes more granular, such as the case of the impact of diseases of poorly known ants, bees and wasps, fewer controls exist.

“In a country like New Zealand, where our conservation is hugely valued, it’s important to invest heavily in biosecurity and act proactively. However, we are also a trading nation and striking a balance between trade and conservation goals can be difficult.”

Evan studied for a Bachelor of Science and a Bachelor of Laws before completing his PhD. His expertise in both areas meant he was able to examine the interface between biology and policy.

“Science is about empirical hypothesis testing, whereas in law you’re building a coherent argument based on legal precedent—so they’re quite different academic disciplines. That was interesting because it made me look at problems in very different ways,” he says.

Evan now works at the Ministry of Primary Industries in the regulation of agricultural chemicals.